title: Evidence for two different regulatory mechanisms linking replication and segregation of vibrio cholerae chromosome II.
abstract: Understanding the mechanisms that coordinate replication initiation with subsequent segregation of chromosomes is an important biological problem. Here we report two replication-control mechanisms mediated by a chromosome segregation protein, ParB2, encoded by chromosome II of the model multichromosome bacterium, Vibrio cholerae. We find by the ChIP-chip assay that ParB2, a centromere binding protein, spreads beyond the centromere and covers a replication inhibitory site (a 39-mer). Unexpectedly, without nucleation at the centromere, ParB2 could also bind directly to a related 39-mer. The 39-mers are the strongest inhibitors of chromosome II replication and they mediate inhibition by binding the replication initiator protein. ParB2 thus appears to promote replication by out-competing initiator binding to the 39-mers using two mechanisms: spreading into one and direct binding to the other. We suggest that both these are novel mechanisms to coordinate replication initiation with segregation of chromosomes.
authors.affiliation: Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Venkova-Canova
authors.forename: Jong Hwan
authors.initials: JH
authors.lastname: Baek
authors.forename: Peter C
authors.initials: PC
authors.lastname: Fitzgerald
authors.forename: Melanie
authors.initials: M
authors.lastname: Blokesch
authors.forename: Dhruba K
authors.initials: DK
authors.lastname: Chattoraj
mesh_terms: D002771:Cholera / Q000235:genetics / Q000382:microbiology; D020090:Chromosome Segregation / Q000235:genetics*; D002876:Chromosomes, Bacterial / Q000235:genetics*; D004265:DNA Helicases; D004261:DNA Replication / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D006801:Humans; D015534:Trans-Activators; D014734:Vibrio cholerae / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D015534:Trans-Activators; C045264:replication initiator protein; D004265:DNA Helicases